title: Kupffer cells and activation of endothelial TLR4 coordinate neutrophil adhesion within liver sinusoids during endotoxemia.
abstract: A key pathological feature of the systemic inflammatory response of sepsis/endotoxemia is the accumulation of neutrophils within the microvasculature of organs such as the liver, where they cause tissue damage and vascular dysfunction. There is emerging evidence that the vascular endothelium is critical to the orchestration of inflammatory responses to blood-borne microbes and microbial products in sepsis/endotoxemia. In this study, we aimed to understand the role of endothelium, and specifically endothelial TLR4 activation, in the regulation of neutrophil recruitment to the liver during endotoxemia. Intravital microscopy of bone marrow chimeric mice revealed that TLR4 expression by non-bone marrow-derived cells was required for neutrophil recruitment to the liver during endotoxemia. Furthermore, LPS-induced neutrophil adhesion in liver sinusoids was equivalent between wild-type mice and transgenic mice that express TLR4 only on endothelium (tlr4(-/-)Tie2(tlr4)), revealing that activation of endothelial TLR4 alone was sufficient to initiate neutrophil adhesion. Neutrophil arrest within sinusoids of endotoxemic mice requires adhesive interactions between neutrophil CD44 and endothelial hyaluronan. Intravital immunofluorescence imaging demonstrated that stimulation of endothelial TLR4 alone was sufficient to induce the deposition of serum-derived hyaluronan-associated protein (SHAP) within sinusoids, which was required for CD44/hyaluronan-dependent neutrophil adhesion. In addition to endothelial TLR4 activation, Kupffer cells contribute to neutrophil recruitment via a distinct CD44/HA/SHAP-independent mechanism. This study sheds new light on the control of innate immune activation within the liver vasculature during endotoxemia, revealing a key role for endothelial cells as sentinels in the detection of intravascular infections and coordination of neutrophil recruitment to the liver.
authors.affiliation: Director, Snyder Institute for Chronic Disease, Dept. of Physiology and Pharmacology, Univ. of Calgary, Alberta, Canada, 3330 Hospital Dr. NW, Calgary, AB, T2N 4N1, Canada. pkubes@ucalgary.ca.
authors.forename: Braedon
authors.initials: B
authors.lastname: McDonald
authors.forename: Craig N
authors.initials: CN
authors.lastname: Jenne
authors.forename: Lisheng
authors.initials: L
authors.lastname: Zhuo
authors.forename: Koji
authors.initials: K
authors.lastname: Kimata
authors.forename: Paul
authors.initials: P
authors.lastname: Kubes
mesh_terms: D000510:Alpha-Globulins / Q000378:metabolism; D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002448:Cell Adhesion; D042783:Endothelial Cells / Q000276:immunology* / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D019446:Endotoxemia / Q000276:immunology* / Q000378:metabolism; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism; D006820:Hyaluronic Acid / Q000378:metabolism; D007113:Immunity, Innate; D007728:Kupffer Cells / Q000276:immunology* / Q000378:metabolism; D008099:Liver / Q000098:blood supply / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000510:Alpha-Globulins; C476399:Cd44 protein, mouse; D018960:Hyaluronan Receptors; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C011877:inter-alpha-inhibitor; D006820:Hyaluronic Acid
keywords: TLR4; inflammation; leukocyte recruitment; lipopolysaccharide